Present height adjustable piece of furniture that is driven by an electric motor is usually powered via a mains power supply. When the electric motor is operated it consumes the power supplied to the piece of furniture. A height adjustable piece of furniture is rather seldom operated. The piece of furniture may typically be operated a few times a day. Most of the time the piece of furniture is not in use and operation circuits in the piece of furniture is in a stand-by mode.
In the stand-by mode the piece of furniture still consumes power due to detection circuits adapted to detect operation of an operation button for activating the electric motor. A plurality of solutions has been disclosed trying to alleviate the drawback of stand-by power consumption by minimizing the stand-by power of the piece of furniture. For instance in WO11134612 A2, which discloses a control circuit for adjustable piece of furniture wherein the connection to the mains power supply is disconnected in a stand-by mode. However, there is still power consumption in the piece of furniture in the stand-by mode due to a detection circuit. Also a very small amount of power consumption during stand-by mode accumulates to large power consumption over time, due to the fact that the piece of furniture is connected to the power supply constantly.
One way of reducing the power consumption from the mains power supply during a stand-by mode is disclosed in WO10054656 A1. A height adjustable piece of furniture is disclosed comprising a solar panel and an energy storage unit. In the stand-by mode, the mains power supply is disconnected and the power needed by the detection circuit is provided by the energy storage, which has been charged by the solar panel. The piece of furniture may thereby be completely disconnected from the mains power supply during stand-by mode. When a button is activated for operation of the electric motor, the piece of furniture is connected to the mains power supply for powering the electric motor. Hence, there is still a need for power in the stand-by mode, but which power is provided off-mains. A solar panel is an expensive and complex solution to the problem of needing mains power supply in stand-by mode. Further it does not solve the problem of needed power level during stand-by mode.
Consequently, there is a need for a solution of powering a height adjustable piece of furniture, which provides further less power needs during a stand-by mode in order to reduce power consumption.